I am Joel Sánchez. I received my bachelor degree from the Tecnológico de Monterrey Campus Toluca in México (2004-2008). Afterwards, I did a Master in Physics and Mathematics at the Universidad de Granada, in Spain (2009-2010). As part of my master's research work, I studied the helical trayectory of the relativistic jet of 4C39.25, under the supervision of Dr. Antxon Alberdi. I carried my PhD thesis under the supervision of Dr. Rainer Schödel and Dr. Antxon Alberdi at the IAA-CSIC. The topic of my dissertation (2010-2015) was the study of the following physical aspects of massive stars:  

Multiplicity in massive stars: Multiplicity is a characteristic property of massive stars, since around 90% of them belong to a multiple system. This property can provide important clues to massive star formation. For this project, I obtained optical interferometric observations with AMBER at the Very Large Telescope Interferometer (VLTI) of two massive triple hierarchical systems, HD150136 and Herschel36. I performed model fitting to the interferometric observables and image reconstruction. As a result, for the first time, the tertiary components were resolved in both systems and a first-order determination of the outer orbit was given. These projects represent the first step to test for coplanarity in order to obtain information of the formation of the systems. 

Interactions of massive stars with the ISM: I studied the bright massive stars with bow-shock structure at the inner parsec of the Galactic Center (GC). To perform this research I used near-infrared Sparse Aperture Masking (SAM) observations and direct Adaptive Optics images obtained with the Very Large Telescope. As a result: i) I developed a novel method to calibrate SAM data in crowded fields; ii) the 3D position and geometry of the bow-shock shells where determined via a steady state radiative transfer model; iii) the mechanisms of the near-infrared bow-shock emission were characterized; finally, using a Monte-Carlo simulation, the possible orbital planes of the bow-shock sources around the massive black hole SgrA* were estimated, adding new observational evidence for the existence of an isotropic distribution of massive stars at the GC.

Massive young stellar objects (MYSOs): Observations of the early phases in massive stars are challenging, particularly because young high-mass stars are highly opaque by the large amount of gas and dust of their parental clouds. The contemporary massive star formation theories suggest the presence of disk-like structures at the core of MYSOs. However, these structures have been elusive for very massive YSOs. Therefore, the study of individual objects where such disks may be observed is of astrophysical importance. I study the young stellar object NGC3603 IRS9A* with NACO/SAM observations and long-slit CRIRES spectroastrometric data. These new interferometric data confirmed the previously predicted disk at the core of IRS9A, and improved considerably previous estimates of its size and orientation.

I built a state-of-the-art radiative transfer model, which reproduces the brightness distribution observed at mid- and near- infrared interferometric observations, and the spectral energy distribution. This model includes a system composed of a hot-disk and an outer envelope with bipolar cavities and it is able to reproduce consistently the observed interferometric visibilities. Nevertheless, my results reveal that the core of MYSOs is complex and more detailed models, which include binarity, gaps and disk inhomogeneities, may be required. 

Currently, I am interested on the study of young stellar objects, not only at the high-mass regime but also at low- and intermediate-mass scales. Specifically, I am focused in simultaneous modeling of interferometric observables (not only in the infrared domain but also at millimeter and radio wavelengths) and the spectral energy distribution of YSOs to build a comprehensive framework of their morphology. A short-term forecoming project is the complete characterization of the disk at the core of IRS9A using long-baseline optical and millimeter interferometry in combination with radiative transfer models. However, I consider it important to expand this kind of studies to other targets. Additionally, my current projects also include the complete determination of the orbits in the massive multiple systems HD150136 and Herschel36 with new infrared long-baseline interferometry and spectroscopic data.

Furthermore, the new generation of extreme AO-assisted cameras, the improvements in the current infrared instruments (e.g., aperture masking in VISIR/VLT, the new Vortex mask coronagraphy at NACO/VLT, Keck/NIRC2), and the new infrared long-baseline interferometers (e.g., PIONIER/VLTI, GRAVITY/VLTI) open an opportunity to expand my research to the detection and characterization of low-mass companions around high-mass stars. Technically, I am interested in the development of software to optimize the data reduction of sparse aperture masking, Kernel phases, coronagraphy and long-baseline interferometry, techniques especially useful for high contrast imaging. Finally, I am interested in the development of new algorithms to perform image reconstruction for interferometric data.